The minister responsible for setting up the Independent Broadbased Anti-Corruption Commission (IBAC), Andrew McIntosh, said the body would have the power to investigate cases retrospectively when it starts next year.

Asked if the opposition could call on IBAC to investigate Mr Overland's sudden resignation, Mr McIntosh said, "Anybody, including the Labor Party, can make a complaint to IBAC."

Mr McIntosh said IBAC would then decide whether or not to investigate the complaint.

"It certainly won't be a matter for the government, it certainly won't be a matter for the opposition," he told reporters.

IBAC will take control of the Office of Police Integrity (OPI) and investigate corruption within police and the public sector at large.

Mr McIntosh criticised a lack of "proper oversight" of the OPI and said IBAC would eradicate that problem.

The Victorian ombudsman is believed to be investigating the OPI over claims it abused its powers by tapping the phone of former deputy commissioner Ken Jones.

Asked if IBAC could have helped prevent the ongoing crisis in police command, Mr McIntosh said Victoria had lagged behind other states in setting up an effective anti-corruption regime.

"As we've seen in other states, there is a powerful inspector (running anti-corruption commissions), there's also a powerful body, a parliamentary committee, oversighting," he said.

"That's what it should be. We don't have it in this state, and that has probably been a significant problem with the OPI."

Mr McIntosh, who is also Minister for Crime Prevention and Minister for Corrections, said he'd had a good working relationship with Mr Overland.

"I found him very good to deal with, always accessible and indeed had no difficulties with Simon."